2,246 Works

Adsorption–strain coupling at solid surfaces

Jörg Weißmüller
This brief review inspects how chemistry or electrochemistry at a solid–vapor or solid–electrolyte interface couple to the mechanics of the solid. Emphasis is on the complementarity of two at first sight unrelated phenomena: on the one hand, adsorption or electric charging change the local tangential stresses in the solid surface; on the other hand, a tangential strain of the surface changes the adsorption enthalpy and the chemical or electric potential. One and the same materials...

Carbon nanoparticles’ impact on processability and physical properties of epoxy resins : a comprehensive study covering rheological, electrical, thermo-mechanical, and fracture properties (mode I and II)

Hauke Meeuw, Johann Körbelin, Valea Kim Wisniewski, Ali Shaygan Nia, Adrián Romaní Vázquez, Martin Rudolf Lohe, Xinliang Feng & Bodo Fiedler
A trade-off between enhancement of physical properties of the final part and the processability during manufacturing always exists for the application of nanocarbon materials in thermoset-based composites. For different epoxy resins, this study elaborates the impact of nanocarbon particle type, functionalization, and filler loading on the resulting properties, i.e., rheological, electrical, thermo-mechanical, as well as the fracture toughness in mode I and mode II loading. Therefore, a comprehensive set of carbon nanoparticles, consisting of carbon...

Modeling of delamination during milling of unidirectional CFRP

Wolfgang Hintze & Dirk Hartmann
The production of CFRP needs edge trimming in order to remove burrs as well as undefined orientated fibres and to shape the final part contour. Edge trimming is usually done by contour milling. The quality of machined edges may be affected by fibre protrusions and delaminated fibres which cause manual repair or may even lead to scrap. Delamination of fibres is often initiated by stresses applied during engagement of the cutting edge. Based on measured...

Residue - and by-product based bioresources - characterization, properties and pathways

Ina Körner, Saskia Hertel, Moses Ogun, Steffen Walk, Jessica Schermuly, Phillipp Lüssenhop & Stefan Deegener

Bioimpedance analysis of L929 and HaCaT cells in low frequency range

Viviane S. Teixeira, Jan-Patrick Kalckhoff, Wolfgang Krautschneider & Dietmar Schröder
In this work, Bioimpedance Spectroscopy (BIS) is used to study fuids and cell solutions. A new four-electrode-terminal (4T) chamber using 3D printing and stainless steel corrosion resistant V4A was designed to measure the impedance of live cell solutions at the frequency range 0.1Hz-1MHz. At f < 1kHz the double layer (DL) that builds at electrode's surface raises the impedance substantially preventing the observation of the real impedance of the cells. The new 4T design circumvents...

Influence of application parameters of ultrasonic-assisted bone instruments on the tear force of a substitute material for spinal dura mater

Marie C. Foelkel, Vitali Herzog, Markus Meier & Michael M. Morlock
An ultrasonic-assisted bone instrument can be used for the dissection of bone in spinal surgery. During surgery, the tip of such a bone instrument can touch spinal dura mater. Especially during critical re-operations, high forces can be unintentionally applied on spinal dura mater. To prevent dural tears, the influence of application parameters on the tear force shall be analyzed. Collagen foil is used as a substitute material for spinal dura mater because of its similar...

Primary hip replacement stem taper fracture due to corrosion in 3 patients

Michael Morlock, Dennis Bünte, Harmen Ettema, Cees C. Verheyen, Åke Hamberg & Jeremy Gilbert

Evaluating the performance of solvers for integer-linear programming

Arno Luppold, Dominic Oehlert & Heiko Falk
Optimizing embedded systems often boils down to solving complex combinatorial optimization problems. Integer-Linear Programming (ILP) turned out to be a powerful tool to solve these problems, as beyond traditional constraints, Boolean variables may be used to model complex logical expressions and conditionals. One of the key technical aspects is to be able to efficiently express these relations within the ILP. This paper presents formalized solutions for these issues, as well as an assessment of common...

Draft genome sequence of type strain Clostridium pasteurianum DSM 525 (ATCC 6013) : a promising producer of chemicals and fuels

Sugima Rappert, Lifu Song, Wael Sabra, Wei Wang & An-Ping Zeng
Clostridium pasteurianum, an anaerobic bacterium able to utilize atmospheric free nitrogen for biosynthesis, has recently been proven to be a promising producer of chemicals and fuels, such as 1,3-propanediol and n-butanol. Here, we report the high-quality draft genome sequence of DSM 525, a type strain of C. pasteurianum.

Integration of oxygen-containing exhaust gas into the air separation unit of an oxyfuel power plant

Jens Dickmeis & Alfons Kather
The Oxyfuel process is one possible solution to lower the high specific CO2 emissions of coal-fired power plants. The flue gas generated by this process has a high CO2 content, due to the missing nitrogen. However the dried flue gas still contains approximately 15 vol% (dry) impurities (NOx, SOx, O2, N2 and Ar). To further increase the CO2 purity the flue gas needs to be treated in a gas processing unit (GPU). Additional downstream gas...

Concurring urbanizations? Understanding the simultaneity of sub-and re-urbanization trends with the help of migration figures in Berlin

Lin Hierse, Henning Nuissl, Fabian Beran & Felix Czarnetzki
Most classical models of urban development conceptualize suburbanization and reurbanization as opposing processes of in-and out-migration. The article at hand starts from the understanding that this linear interpretation of migration figures falls short of the mark. Drawing on different approaches to op-erationalize reurbanization, case-specific migration-data from Berlin illustrates a population development where decline and revival do not exclusively happen at either the urban core or the city’s fringes, but can be observed throughout the city...

Dynamic simulation of different transport options of renewable hydrogen to a refinery in a coupled energy system approach

Lisa Andresen, Carsten Bode & Gerhard Schmitz
Three alternative transport options for hydrogen generated from excess renewable power to a refinery of different scales are compared to the reference case by means of hydrogen production cost, overall efficiency, and CO2 emissions. The hydrogen is transported by a) the natural gas grid and reclaimed by the existing steam reformer, b) an own pipeline and c) hydrogen trailers. The analysis is applied to the city of Hamburg, Germany, for two scenarios of installed renewable...

Effect of processing route on the microstructure and mechanical properties of hot work tool steel

Robert Besler, Markus Bauer, Kaline Pagnan Furlan, Aloisio Nelmo Klein & Rolf Janßen
Powder metallurgy is a growing sector in industrial production, as it offers outstanding energy, cost and material savings in comparison with established processing routes such as casting. Hot work toll steels are usually produced by ingot metallurgy, but also by powder metallurgy, namely hot isostatic pressing and powder forging routes. In this paper we investigate the possibility of production of a hot work tool steel (AISI H13) by conventional (die compaction and pressureless sintering) and...

Near-field radiative heat transfer with hyperbolic metamaterials

Slawa Lang
Max Plancks bedeutende Schwarzkörper Theorie kann den Anstieg der strahlenden Wärmeübertragung zwischen eng aneinanderliegenden Körpern, bekannt als Nahfeld Wärmeübertragung, nicht erklären. Wir demonstrieren diesen Effekt mit Hilfe einer neuen, dynamischen Messmethode und messen Wärmeströme bis zu 16-mal größer als die Schwarzkörper Grenze. Wir zeigen, dass thermische Strahlung in hyperbolischen Metamaterialien (HMMs) – äußerst anisotropen Nanostrukturen – sehr stark ist und ihre Eigenschaften sich von Schwarzkörper Strahlung deutlich unterscheiden. Schließlich erweisen sich Nahfeld Wärmeströme zwischen HMMs...

Mikrostrukturelle Betrachtung des Einflusses von Poren auf die mechanischen Eigenschaften von faserverstärkten Kunststoffen

Wilfried Liebig
Die vorliegende Arbeit befasst sich mit der Untersuchung des Einflusses von Poren auf die mechanischen Eigenschaften von Faser-Kunststoff-Verbunden (FKV) unter Drucklast. Um die Schadensentwicklung durch Poren in einem FKV näher be\-schrei\-ben zu können, wurde der komplexe dreidimensionale strukturelle Aufbau des Verbundes inklusive der Poren analysiert und dieser in einen vereinfachten modellhaften Verbund überführt. Der modellhafte Verbund besteht aus der Matrix und mindestens zwei Fasern, zwischen denen eine einzelne Pore platziert wurde. Neben der experimentellen Untersuchung...

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